Lately my truck has been smoking a lot. I'm am really struggling to figure out if its just running rich or if its burning oil.

The motor has about 10k on a complete rebuild. It was my first rebuild ever and I didn't break it in as well as I should have. Its also had an oil leak for a while and I'm ashamed to say I have run it pretty darn low on oil on a few occasions. Never lost oil pressure though!

The smoke is black if I floor the pedal - definently rich then. But if I rev it gently its just grey, with maybe a hint of blue, but its not clear cut blue oil smoke.

Compression when cold:
1: 160psi
2: 165psi
3: 160psi
4: 150psi (this goes to 165psi if I squirt some oil in)

So clearly the #4 rings are worn a little, but is that enough to give a steady flow of smoke?


Thanks,

Scerb

If the motor used so much oil that it ran low a couple of times in 10k miles I'd say you have your answer; You're burning oil! Of course you might be running rich as well. Is this the truck with the Webber carb?

When my '84 22R had only 65k miles it used a half a quart of oil every 3000 miles. Those were the good old days. --- Matt



you have to add oil so often that you sometimes let it get a little

valve seals are bad, real common

I'm guessing/hoping valve seals as well. I think Ima try and do them without pulling the head. I'll get an air attachment for the spark plug holes, shouldn't be TOO bad.

I think I'd rather do the old trick where you feed rope into the spark plug hole and (gently) bring things to TDC. Drop one of those valves and you are royally screwed.

Supposedly pressurizing the cylinder works well. Anyone have any personal experience with this?

I've done the rope method and say its foolproof. So its me proof.

Did you replace the valve seals when the rebuild was done? If you did, did you slide the seal on the valve using a thin piece of cellophane? If you just slid them on the valves, you probably nicked the seal.

Always lubricate a seal and protect the seal lip when installing them. It takes a little more time but a lot less time then doing it over.
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>>>*The description really doesn't fit valve stem oil seals well as the culprit. Typically valve seals will cause the engine to pass light blue smoke at idle, coming down under compression, (like coasting down a long hill) or when the throttle is jazzed.

Plus unless the seals are gone or shot the engine still won't use a huge amount of oil, perhaps if a guide or two were very bad maybe. Very badly loose valve guides are a bit rare on this design, too.

The rich condition is the key here and the black smoke is an indicator. A rich running engine will use oil even when the rings are in perfect condition, this becomes noticeable on any long trip as "sudden" oil use since the evaporative system will draw out the lighter fuel molecules.

Overly rich conditions means fuel in the oil, the oil rings cannot control diluted oil. Plus remember you can take the oil rings completely off the piston and the other two rings will give close to normal compression. Thus a compression test is a good indicator of long term wear but not for upset conditions.

My best guess is the oil rings are weak, I say this because of the comment about running low a few times. The oil wiper rings don't last very long without lube, once they get overheated from friction, they will lose tension.

If I am right there is only one fix, replace them. Then fix the rich condition too.....*EB

I was told by a friend that you gotta be carefull when installing the timing chain so that u dont nick a head gasget.. maybe u nicked the gasget and oil is leaking into the number 1 cyl, causinga little bit more compression.. just a though